Arctic island

ABSTRACT

A man-made island and a method for constructing the same in an ice covered body of water using portions of the ice sheet as integral parts of the island. The island is formed by placing fill material, such as sand or gravel, on a portion of the ice sheet to ground that portion. The grounded ice sheet is cut free from the surrounding ice sheet and matter, such as fill material, blocks of ice, etc., is placed on the grounded portion of the ice sheet to construct an island in the body of water. Additional portions of the ice sheet can be separated and grounded on top of previously grounded portions prior to placing matter on the stack of grounded ice pieces to construct the island.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method for constructing an island in anice-covered body of water using the natural sheet of ice as an integralpart of the island.

2. Description of the Prior Art

In shallow water polar regions, which are covered with a sheet of ice atleast a part of the year, man-made islands have proven to be anadvantageous structure to use as a base for oil-field operations. Suchman-made islands have been used as bases for exploratory oil welldrilling operations and will be used as well for oil production relatedoperations. To survive the harsh environmental conditions of the arctic,these islands must be protected against erosion and overtopping by wavesand storm tides during the summer and, during the winter, they must beable to withstand significant lateral loads exerted by movement of thesurrounding sheet of ice.

Islands constructed in shallow water regions off the northern coast ofCanada have been built entirely of fill material, such as gravel andsilt. Most of those islands were built during the summer while there wasno ice cover. At least one was built in winter by removing a section ofthe sheet of ice which had formed on the body of water and dumping fillmaterial directly on the bottom. These all-fill-material islands havecertain limitations. In certain polar regions, a sufficient quantity offill material is not readily available and must be transported greatdistances to the island construction site. Moving the vast amount offill material needed to construct an island great distances in thearctic is very expensive. Even when fill material is available near theisland construction site, dredging or mining operations in the arcticare expensive.

SUMMARY OF THE INVENTION

The present invention can be seen to offer a method for constructing anisland in polar regions which saves both time and money. This methoduses the natural ice cover as an integral part in the construction ofthe island and thereby lessens the amount of fill material needed.

Briefly, the method of the present invention comprises the step ofplacing fill material upon the natural ice sheet floating on the body ofwater until the ice has grounded on the bottom of the body of water. Theplacing of fill material upon the ice is continued until a workingplatform of the freeboard, i.e., elevation above the water, and sizedesired is achieved. It will be preferred to cut the submerged layer ofice free from the surrounding ice either before or after the fillmaterial has grounded the ice sheet.

Another embodiment for constructing an island according to the presentinvention comprises placing at least enough fill material on a floatingpiece of ice to overcome its buoyancy, lowering it to the desiredlocation on the bottom of the body of water, moving another floatingpiece of ice of the desired size above the grounded piece and placingenough fill material on the second piece of ice to sink it on top of thefill material on the first piece of ice. This procedure can becontinuously repeated until an island of the desired size and of thedesired elevation, up to the water level, has been built. The desiredfreeboard can be built with additional fill material and ice. Once theisland has been constructed, it will be preferred to provide some typeof slope protection around the sides of the island to minimize damage tothe island caused by erosion and ice features moving against it. Toprotect against settling, insulation and refrigeration devices, such asheat pipes and air convection piles, can be used to keep the ice layersof the island frozen.

The present invention can be seen to offer significant advantages in theconstruction of man-made islands in polar regions by using the naturalice cover as an integral part of the island.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-4 are elevation views of an arctic body of water and an islandin cross-section illustrating the steps of the method of constructingthe island according to one embodiment of the present invention.

FIGS. 5-9 are elevation views of an arctic body of water and an islandin cross-section illustrating the steps of the method of constructingthe island according to another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Briefly, the method of the present invention for constructing a man-madeisland in polar regions comprises the step of placing fill material,which material is denser than the water, upon the naturally-occurringsheet of ice until the sheet of ice is grounded on the bottom of thebody of water.

FIGS. 1 through 4 illustrate the steps of the method according to oneembodiment of the present invention. FIG. 1 depicts a typicalcross-section of a shallow polar body of water. A sheet of ice 1 isshown floating on top of the body of water 2. The floor or bottom of thebody of water is indicated by the numeral 3.

IN FIG. 2, fill material 10 has been placed upon the natural sheet ofice 1 and the weight of the fill material 10 has caused the sheet of ice1 to bend and ground on the floor 3 of the body of water 2. The fillmaterial will generally have a density greater than that of the body ofwater and can be a material such as gravel or silt. The fill materialcan possibly be dredged or mined from nearby locations, or elsetransported to the island construction site by barge or truck.

In FIG. 3, the portion of the sheet of ice that is grounded has been cutfree from the surrounding sheet of ice. Such cutting of the ice can bedone prior to any fill material 10 being placed on the sheet of ice orat any later time.

Additional fill material 10 has been placed on the grounded sheet of icein FIG. 4. The additional fill material 10 has built the island up toachieve the desired working area and freeboard. The sides of theman-made island have been protected to minimize damage to the islandcaused by erosion and by the surrounding sheet of ice moving against theisland by slope protection apparatus 11. The slope protection apparatus11 can be a number of items including large pieces of rock, sand bags,or a concrete revetment. In circumstances where the island will only beused for a very short time, and the rate of erosion is minimal, it maybe acceptable to leave the sides of the island unprotected. It shouldalso be noted that the slope protection apparatus depicted in FIG. 4 issloped. This slope will assist in breaking up the surrounding ice sheetas it moves against the island. The degree of slope in any specificapplication will depend on various design and environmentalconsiderations.

FIGS. 5 through 9 illustrate another embodiment of the presentinvention. Depicted in FIG. 5 is a sheet of ice 20 floating on a body ofwater 21. Piles 30 have been driven into the floor 22 of the body ofwater 21 to assist in the construction of the island. A thin layer offill material 40 is placed on the sheet of ice 20. The fill material 40should generally have a density greater than that of the water 21.Suitable materials would include gravel and silt. The amount of fillmaterial 40 placed upon the layer of ice 20 should preferably be no morethan would barely allow the sheet of ice 20 to remain floating at thesurface of the body of water 21. Preferably, the fill material 40 issaturated with water and allowed to freeze to bond the fill material 40to the sheet of ice 20. The cold winter temperatures of the arcticwinter will require only a short period of time to freeze the water.

Once the saturated fill material 40 has frozen to the sheet of ice 20, apiece of the ice sheet 20a of the desired dimension is cut free from thesurrounding sheet of ice 20. The piece of ice sheet 20a is positionedover the location where it is to rest on the floor 22 of the body ofwater 21. Additional fill material 40 is placed upon the piece of icesheet 20a to overcome its buoyancy and sink it.

In FIG. 6, the piece of ice sheet 20a is being sunk. Piles 30 andwinching apparatus 31 are used to control the descent of ice piece 20aand guide it to the proper location on the floor 22 of the body of water21. Then the next piece of ice sheet 20b is cut free from thesurrounding sheet of ice 20. It is positioned over the first ice piece20a, see FIG. 7. Additional fill material is placed upon the piece ofice sheet 20b to overcome its buoyancy. The piles 30 and winchingapparatus 31 control the descent of ice piece 20b and guide it to theproper location atop fill material 40 on ice piece 20a, see FIG. 8.

The above enumerated steps are continuously repeated until the stack ofice and fill material has reached the desired elevation above the floor22 of the body of water 21 or, at most, the surface of the body ofwater. Any number of stacks can be built next to each other to achievean island of the desired dimension. As an alternative to stacking eachpiece of ice directly on top of one other piece, the pieces of ice canbe positioned on top of each other in a staggered or offset manner. InFIG. 9, ice pieces 23a and 23b are stacked with each upper piece beingdirectly on top of each lower piece and ice piece 23c is positioned ontop of ice piece 23b in a staggered or offset manner.

Once the desired elevation is achieved, or the water line is reached, itwill be necessary to add additional matter atop the stack of ice andfill material to form a working area having the desired freeboard.Building the island up above the water line can be accomplished by anynumber of methods. For instance, fill material can be placed on top ofthe stack until a working area of the desired dimension and freeboard isachieved. Alternatively, blocks of ice can be cut from the surroundingsheet of ice and placed on top of the stack until the desired workingarea is constructed. Another alternative would be repeatedly spraying orflooding water on top of the stack and allowing it to freeze. Naturally,it is possible to combine the preceding alternatives to build the islandup until it has a working area of the desired dimension and freeboard.FIG. 9 depicts a combination of these three alternatives. A layer of iceblocks 24 have been placed on top of the top ice layer 23e. Ice layer 25was built by repeatedly flooding water on top of the ice blocks 24 andallowing the cold winter temperatures to freeze the water. On top of allthis, additional fill material 40 has been placed.

As in the previous embodiment, slope protection 41, such as rocks, sandbags or a concrete revetment, can be placed around the sides of theisland to slow erosion of the island and assist in resisting the forcesexerted on the island by the surrounding sheet of ice 20 as that icesheet moves against the island.

If fill material 40 completely covers the ice layers, it will act asinsulation and retard the thawing of the ice layers. Even so, in certaincircumstances, it may be desirable to install apparatus to keep the icefrozen. Such apparatus would include air convection piles 51, heat pipes50 (both depicted in FIG. 9) and refrigeration equipment 52 (depicted inFIG. 4). If these units extend a sufficient distance down into theisland, they will freeze, and thereby bond, the island to the floor ofthe body of water to assist the island in resisting the lateral forcesexerted on it by the surrounding ice sheet as it moves against theisland. The desirability of refrigeration and choice of method willdepend on many factors including the amount of insulation surroundingthe ice layers, the temperatures of the water and the air and thedesigned life of the island.

In constructing an island according to the second embodiment, severalvariations are possible. It may be desirable at times to position thetop piece of ice over the stack before placing any fill material on itto insure sufficient clearance between it and the top of the stack.Otherwise, in certain circumstances, the ballast of the layer of fillmaterial on the top piece of ice will increase the ice piece's draft tothe point where it will collide with the stack of ice and fill materialwhen an attempt is made to position the top piece above the stack. Alongthese same lines, each piece of ice could be cut and positioned at thewater's surface before any fill material is placed on it. Anothervariation would be to freeze a thick layer of saturated fill material,which completely overcomes each ice piece's buoyancy, to each piece ofice by supporting the pieces at the surface until the cold air hasfrozen the saturated fill material.

It can be seen that islands constructed according to the presentinvention can reduce both the cost and the time of constructing islandsby decreasing the needed amount of fill material through the use of theice sheet as an integral part of the island.

Although this dislcosure is directed to using the natural sheet of ice,nearly any ice formation may be successfully used as an integral part ofa man-made island. Other variations and changes may be made in theisland and method for constructing it as shown and described hereinwithout departing from the scope of the invention as defined in theclaims.

What is claimed is:
 1. A method for constructing an island in a body ofwater having an ice sheet floating thereon which comprises:placingsufficient fill material having a density greater than the water on afirst piece of the ice sheet which is to become an integral part of theisland to round the first piece; separating the first piece from thesurrounding ice sheet; placing an amount of fill material having adensity greater than the water on a second piece of the ice sheet whichis to become an integral part of the island, said amount of fillmaterial being not more than the amount which allows the second piece ofice to remain floating at the water's surface; separating the secondpiece from the surrounding ice sheet; positioning the second piece overthe grounded first piece; placing additional fill material having adensity greater than the water on the second piece to sink it atop thefirst piece; and placing sufficient matter upon the grounded pieces toconstruct an island.
 2. The method of claim 1 further comprisingrepeatedly conducting the following steps:placing an amount of fillmaterial having a density greater than the water on a piece of the icesheet which is to become an integral part of the island, said amount offill material being not more than the amount which allows the piece ofice to remain floating at the water's surface; separating the piece fromthe surrounding ice sheet; positioning the piece at the water's surfaceover the location where it is to be sunk; and placing additional fillmaterial having a density greater than the water on the piece to sinkit.
 3. The method of claim 1 further comprising saturating the fillmaterial placed on top of each piece and maintaining each piece at thewater's surface until the saturated fill material has frozen to thepiece.
 4. The method of claim 1 further comprising guiding each piece toa precise submerged location with piles and winching apparatus.
 5. Themethod of claim 1 further comprising protecting the sides of the islandwith slope protection apparatus to minimize damage to the island causedby erosion and by the surrounding sheet of ice moving against theisland.
 6. The method of claim 1 further comprising refrigerating thepieces which have been sunk to maintain the ice thereof in a frozenstate.
 7. The method of claim 1 further comprising bonding the island tothe bottom of the body of water by freezing the island thereto withrefrigeration apparatus.
 8. The method of claim 1 further comprisingplacing blocks of ice upon the grounded pieces to assist in constructingan island.
 9. The method of claim 1 further comprising freezing waterupon the grounded pieces to assist in constructing an island.
 10. Themethod of claim 1 further comprising placing fill material upon thegrounded pieces to assist in constructing an island.
 11. An offshoreisland constructed in a body of water having an ice sheet floatingthereon comprising:a first portion of the ice sheet; fill materialpositioned above the first portion of the ice sheet in an amountsufficient to ground the first portion of the ice sheet; a secondportion of the ice sheet positioned above the first portion of the icesheet and separated therefrom by a layer of fill material; andadditional fill material positioned above the second portion of the icesheet in an amount sufficient to ground the second portion of the icesheet above the first portion of the ice sheet and result in an islandin the body of water.
 12. The offshore island of claim 11 furthercomprising a means for refrigerating the portions of the ice sheet whichare integral parts of the island.